//https://leetcode.cn/problems/kth-largest-element-in-an-array/

class Solution {
public:
    int findKthLargest(vector<int>& nums, int k) {
        srand(time(0));
        return qsort(nums, 0, nums.size() - 1, k);

    }

    int qsort(vector<int>& nums, int l, int r, int k)
    {
        if (l == r) return nums[l];

        //选取随机数
        int key = getrandom(nums, l, r);
        //数组划分三块
        int i = l, left = l - 1, right = r + 1;
        while (i < right)
        {
            if (nums[i] < key) swap(nums[++left], nums[i++]);
            else if (nums[i] == key) i++;
            else swap(nums[--right], nums[i]);
        }

        int c = r - right + 1, b = right - left - 1;
        if (c >= k) return qsort(nums, right, r, k);
        else if (c + b >= k) return key;
        else return qsort(nums, 0, left, k - b - c);
    }

    int getrandom(vector<int>& nums, int left, int right)
    {
        int r = rand();
        return nums[r % (right - left + 1) + left];
    }
};